Can radiation induced suppression of immune response be overcome by RE stimulants and can this be exploited in vivo for radiotherapy? The experimental system will be the rat bearing a primary fibrosarcoma induced with benzpyrene or methyl cholanthrene. Tumors on the leg will enable localized tumor irradiation and simple surgical removal by amputation. Transplantation of tumor in inbred rats, given no treatment, RE stimulant, radiation, or RE stimulant plus radiation. Test by capacity to reject graded doses of tumor cells. Does local irradiation of the tumor cause release of tumor specific transplantation antigens (TSTA)? We wish to test that X-ray therapy may influence the host reaction to the tumor, not only by its immunosuppressive action, but may cause the release of TSTA into the circulation. The release of such TSTA could be either helpful by stimulating the immune response, or harmful by competing with the tumor cells for immune lymphocytes of serum antibody. Will be tested by preparing antibody to TSTA and assay for TSTA by precipitating with antibody, separate, adsorb against normal tissue, and assay by radioimmunoassay. EXamination of a new class of immune adjuvants: polycations, with separation of their in vivo activity into direct tumoricidal action, and indirect action via RE stimulation. Will test by measuring effect on skin grafts in rats, and effect on growth of syngeneic timur in rats and mice.